Molding processes are commonly used to form plastic articles that are relatively rigid in nature, including containers, medical devices, and so forth. For example, containers for stacks or rolls of pre-moistened wipes are generally formed by injection molding. One problem associated with such containers, however, is that the molding material is often formed from synthetic polyolefins (e.g., polypropylene or HDPE) that are not renewable. Various attempts have thus been made to use renewable polyesters (e.g., polylactic acid (“PLA”)) in these and other applications. However, market penetration of renewable polyesters has been limited due to a density that is approximately 30% higher than conventional polyolefins, which makes them significantly more expensive. To help reduce the density of such polyesters, gaseous blowing agents are sometimes employed to help create a cellular “foamed” structure having a certain degree of porosity. Unfortunately, however, the processability and tensile properties of the resulting cellular structure is often compromised due to the uncontrolled pore size and distribution. Other problems also exist. Renewable polyesters, for example, have a relatively high glass transition temperature and typically demonstrate a very high stiffness and tensile modulus, while having relatively low impact resistance and low ductility/elongations at break. As an example, polylactic acid has a glass transition temperature of about 59° C. and a tensile modulus of about 2 GPa or more. Nevertheless, the tensile elongation (at break) for PLA materials are only about 5%, and the notched impact strength is only about 0.22 J/cm. Such low impact strength and tensile elongation values significantly limit the use of such polymers in injection molded parts, where a good balance between material stiffness and impact strength is required.
As such, a need currently exists for a low density renewable polyester composition that can also demonstrate a high resistance to failure when subjected to stress.